1. Field of the Present Invention
The present invention relates to a thin film magnetic head and, more particularly, to a combined-type thin film magnetic head in which a read magnetoresistive (MR) head having a magnetoresistive device and a write inductive head having a coil layer and a core layer are laminated.
2. Description of the Related Art
FIG. 5 is a perspective view of a conventional thin film magnetic head, FIG. 6 is a sectional view taken along the line 6xe2x80x946 of FIG. 5, FIG. 7 is an enlarged front view observed from a direction indicated by an arrow 7 in FIG. 6, and FIG. 8 is a schematic top plan view observed from a direction indicated by an arrow 8 in FIG. 6. Furthermore, FIG. 9 is a schematic top plan view illustrating a lead-out line pattern of the conventional thin film magnetic head, and FIG. 10 is a top plan view illustrating an upper shield layer and a coil layer of the conventional thin film magnetic head.
A slider 1 of a thin film magnetic head mounted on a magnetic recording device such as a hard disk drive is composed of a ceramic material, e.g. a combination of alumina (Al2O3) and titanium carbide (TiC). The slider 1 has a read end surface 1a facing toward an upstream side of a moving direction of a disk surface of a magnetic recording medium, a trailing end surface 1b facing toward a downstream side, and a rail-shaped ABS surface 1c opposing a disk surface of the slider 1 as shown in FIG. 5. The trailing end surface 1b is provided with a head device 2 and four bonding pads 3 for connection with an external circuit.
The head device 2, which is formed of a thin film, is constituted by a combined-type thin film magnetic head wherein a read magnetoresistive magnetic head (hereinafter referred to as an xe2x80x9cMR headxe2x80x9d) 2a and a write inductive magnetic head (hereinafter referred to as an xe2x80x9cinductive headxe2x80x9d) 2b that is deposited on the MR head 2a as shown in FIG. 6.
Referring to FIG. 6 and FIG. 7, the MR head 2a has a lower shield layer 2a1 formed of a Nixe2x80x94Fe type alloy or a Permalloy, a lower gap layer 2a2 that is formed of a nonmagnetic material such as Al2O3 and deposited on the lower shield layer 2a1, a magnetoresistive (MR) device 2a3 provided in a central portion of an upper layer of the lower gap layer 2a2, an electrode layer 2a4 formed from an upper surface of both ends of the MR device 2a3 through a surface of the lower gap layer 2a2, an upper gap layer 2a5 that is provided on the MR device 2a3 and an upper layer of the electrode layer 2a4 and formed of a nonmagnetic material such as Al2O3, and an upper shield layer 2a6xe2x80x2 that is formed on the upper layer of the upper gap layer 2a5 by plating and is formed of a magnetic material such as a Nixe2x80x94Fe type alloy or Permalloy, all the layers being deposited on a trailing end surface 1b of the slider 1. The MR device 2a3 shown in FIG. 7 illustrates an anisotropic magnetoresistive (AMR) device that is formed of an SAL film Sa, a SHUNT film Sh, and an MR film M having magnetoresistive effect, the films being laminated in this order from the bottom. Furthermore, the electrode layer 2a4 shown in FIG. 7 is comprised of a lower layer that is a hard bias layer H composed of CoPt, CoCrPt or the like, and an upper layer that is an electroconductive layer C composed of chrome (Cr), copper (Cu), or the like. The hard bias layer H applies a bias magnetic field, which is known as a longitudinal bias, to the MR film M in a direction parallel to the film surface thereof. In the MR head 2a, a reading magnetic gap length G1 is decided by a distance between the MR film M and the lower shield layer 2a1 or the upper shield layer 2a6xe2x80x2. A track width Tw is decided by a range wherein sense current flows between the two electrode layers 2a4 at both sides in the MR film M. A giant magnetoresistive (GMR) device may be used as the MR device 2a3.
Referring now to FIG. 6 and FIG. 8, the inductive head 2b includes a lower core layer 2b1xe2x80x2 serving also as the upper shield layer 2a6xe2x80x2 of the MR head 2a, a nonmagnetic material layer 2b2 that is provided above the lower core layer 2b1xe2x80x2 and forms a write magnetic gap G, a coil insulating layers 2b3 and 2b3xe2x80x2 that are deposited on the nonmagnetic material layer 2b2 and composed of an organic resin material or the like, flat spiral coil layers 2b4 that are buried in the coil insulating layers 2b3 and 2b3xe2x80x2 and composed of a low-resistance electroconductive material such as Cu, and an upper core layer 2b5 that has one end thereof in contact with the nonmagnetic material layer 2b2 adjacent to the ABS surface 1c and the other end thereof connected to the lower core layer 2b1xe2x80x2, and is composed of a magnetic material such as a Nixe2x80x94Fe, type alloy or Permalloy.
Referring now to FIG. 8 and FIG. 9, two connecting terminals 10a and 10b that are formed simultaneously and located away from the lower core layer 2b1xe2x80x2 are formed at both sides of the lower core layer 2b1xe2x80x2 and connected to the two electrode layers 2a4 that are connected to both ends of the MR device 2a3. Furthermore, four lead-out lines 4a, 4b, 4c, and 4d formed of a low-resistance electroconductive material such as copper (Cu) are provided on the coil insulating layer 2b3 by being plated thereon at the same time when the coil layers 2b4 are formed. Two lead-out lines 4a and 4b respectively have connection ends 4a1 and 4b1 that oppose both sides of the lower core layer 2b1xe2x80x2 and are conductively connected to the two connecting terminals 10a and 10b, respectively, via contact holes (not shown) provided in the upper gap layer 2a5. The lead-out line 4c, is integrally formed continuously from an outermost circumferential end of the coil layers 2b4. The lead-out line 4d has a connecting end 4d1 at a side of the lower core layer 2b1xe2x80x2 and is connected to a central end N of the coil layers 2b4 via a contact hole (not shown) provided in the coil insulating layer 2b3 by a lead layer 5 provided on the coil insulating layer 2b3 by plating at the same time when the upper core layer 2b5 is formed.
The other ends of the individual lead-out lines 4a, 4b, 4c, and 4d are provided with bump connections 4a2, 4b2, 4c1, and 4d2, and bumps (not shown) formed of a Nixe2x80x94Fe type alloy or Permalloy, or the like are provided thereon. A protective layer 6 formed of Al2O3 or the like is provided on the entire trailing end surface 1b of the slider 1, covering the upper layers, including the upper core layer 2b5, the lead-out lines 4a, 4b, 4c, and 4d and the bumps (not shown), etc. Four bonding pads 3 composed of gold are formed by plating on the upper layers of the four bumps (not shown) that have been partly exposed by polishing the trailing end surface 1b, as shown in FIG. 5 and FIG. 9. Thus, the four bonding pads 3 and the head device 2 are electrically connected to make up the conventional thin film magnetic head.
With an increasing capacity of a magnetic recording device such as a hard disk drive, the slider 1 of a thin film magnetic head is becoming smaller, leading to a necessity for an effective disposition of the bonding pads 3 and the head device 2 in a limited space of the trailing end surface 1b. Regarding the head device 2, a size of the coil layers 2b4 is a decisive factor in determining a size or area of the trailing end surface 1b. In order to place the head device 2 in the limited space, the coil layers 2b4 are formed to have an almost circular shape as shown in FIG. 9 or an elliptic shape which is slightly compressed laterally or in a track width direction, while it is longer in a vertical direction orthogonal to the track width direction or height direction (a direction in which a fringing magnetic field is applied from a magnetic recording medium) as shown in FIG. 10.
According to the shape of the vertically elongated coil layers 2b4, the size of the lower core layer 2b1xe2x80x2, which also serves as the upper shield layer 2a6xe2x80x2, of the inductive head 2b is decided. More specifically, as a dimension of the coil layers 2b4 in the height direction increases, a dimension H in the height direction, rather than a dimension W in the track width direction, of the lower core layer 2b1xe2x80x2 or the upper shield layer 2a6xe2x80x2 must be increased as shown in FIG. 10.
It has been known that most magnetic materials having shapes excluding a spherical shape exhibit xe2x80x9cconfiguration magnetic anisotropyxe2x80x9d in which magnetizing characteristics vary, depending on a direction from a certain point to another arbitrary point. This applies also to the upper shield layer 2a6xe2x80x2 or the lower core layer 2b1xe2x80x2. For instance, when the upper shield layer 2a6xe2x80x2 is formed of a rectangular or elliptic thin sheet with the dimension H in the height direction set to be larger as mentioned above, the upper shield layer 2a6xe2x80x2 develops the configuration magnetic anisotropy. In this case, there is a trend in which an easy axis of magnetization extends in the height direction, i.e. a lengthwise direction, of the upper shield layer 2a6xe2x80x2, while a difficult axis of magnetization extends in the widthwise direction or the track width direction orthogonal with respect to the easy axis.
When the MR head 2a reads magnetically recorded signals from a magnetic recording medium, a fringing magnetic field from the magnetic recording medium opposing the ABS surface 1c enters in the height direction as a signal magnetic field. The height direction of the upper shield layer 2a6xe2x80x2 in which the fringing magnetic field is applied is the easy axis of magnetization as mentioned above, so that a magnetization curve shows a hysteresis indicating an irreversible change.
When a magnetic material has a hysteresis, a microscopic observation reveals that a magnetic domain wall irreversibly moves from a certain position to another position when subjected to a magnetic field. It has been known that the irreversible movement of the magnetic domain wall causes noises called xe2x80x9cBarkhausen noisesxe2x80x9d to occur. Therefore, when the fringing magnetic field that consecutively changes is applied in the height direction that involves the hysteresis when the MR head 2a reads the magnetically recorded signals from the magnetic recording medium, the Barkhausen noises are superimposed together with the signal magnetic field on the MR film M, causing read errors in the MR head 2a. 
Accordingly, the present invention has been made with a view toward solving the problems described above, and it is an object thereof to provide a thin film magnetic head that permits a size of a slider to be reduced and is capable of reducing occurrences of Barkhausen noises caused by configuration magnetic anisotropy of an upper shield layer.
To this end, according to an aspect of the present invention, there is provided a combined-type thin film magnetic head in which a read head that includes a MR device, and an inductive head are laminated, wherein the inductive head has a magnetic material layer having a space for forming at least a coil layer thereon, the magnetic material layer has a front separate layer opposing a magnetic recording medium, a rear separate layer disposed away from the magnetic recording medium with a gap provided relative to the front separate layer, and an upper core layer having one end thereof coupled to a top portion of the front separate layer and also extending onto the coil layer and the other end thereof coupled on a surface opposing the magnetic recording medium via a magnetic gap, the front separate layer serves also as an upper shield layer of a read section and a lower core layer of the inductive head and supports the coil layer in cooperation with the rear separate layer, and a dimension in a track width direction of the front separate layer is larger than a dimension in a direction orthogonal with respect to the track width direction.
Preferably, in the thin film magnetic head in accordance with the present invention, the coil layer is formed over the gap that separates the front separate layer and the rear separate layer so that it is substantially orthogonalized with respect to a lengthwise direction of the gap.
Further preferably, in the thin film magnetic head in accordance with the present invention, the front separate layer is longer than the rear separate layer in the track width direction, and both ends of the front separate layer extend to both sides of the rear separate layer.
Further preferably, in the thin film magnetic head in accordance with the present invention, two lead-out lines that connect the MR device and bonding pads for connection with an external circuit, and connecting terminals for connecting the MR device and ends of the two lead-out lines are located within a range in the track width direction of the front separate layer and provided at both sides of the rear separate layer.
In a further preferred form, the thin film magnetic head in accordance with the present invention is provided with two lead-out lines for connection between the MR device and the bonding pads for connection with an external circuit, and ends of the two lead-out lines connected to the MR device lie within a range of the track width direction of the front separate layer and are provided at both sides of the rear separate layer.